US20030123521A1 - Operating a light emitting diode - Google Patents
Operating a light emitting diode Download PDFInfo
- Publication number
- US20030123521A1 US20030123521A1 US10/300,693 US30069302A US2003123521A1 US 20030123521 A1 US20030123521 A1 US 20030123521A1 US 30069302 A US30069302 A US 30069302A US 2003123521 A1 US2003123521 A1 US 2003123521A1
- Authority
- US
- United States
- Prior art keywords
- led
- current
- pulsing
- depending
- temperature
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
Images
Classifications
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
- H05B45/50—Circuit arrangements for operating light-emitting diodes [LED] responsive to malfunctions or undesirable behaviour of LEDs; responsive to LED life; Protective circuits
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
- H05B45/10—Controlling the intensity of the light
- H05B45/18—Controlling the intensity of the light using temperature feedback
Definitions
- the invention relates to a method for operating a light emitting diode (LED).
- the invention equally relates to a device comprising at least one LED.
- LEDs are well known in the art. LEDs are also employed in a great variety of applications, for example in a display or a keypad lighting of a user interface hardware.
- the intensity of the light emitted by an LED correlates with the level of a supplied current. Additionally, however, the luminous intensity of LEDs is subject to a degradation over time. The degradation rate and therefore the useful lifetime of an LED depends on the power over the LED. The power over the LED, in turn, depends on the forward current supplied to the LED and on the ambient temperature surrounding the LED. Thus, on the one hand, the luminous intensity of an LED supplied with a high current can degrade relatively fast. On the other hand, the luminous intensity of an LED can degrade rather quickly in case of a high ambient temperature, in particular in case of an ambient temperature which is higher than a maximum temperature specified in the respective LED specification.
- the objects are reached with a device comprising at least one LED. It is proposed that the device further comprises a temperature sensing element for measuring the ambient temperature surrounding the at least one LED, and controlling means for controlling a current flowing through the at least one LED depending on the measured temperature.
- the invention proceeds from the idea that the luminous intensity and thus the lifetime of an LED depend in particular on the respective combination of the current through the LED and the ambient temperature. More specifically, a high ambient temperature has less influence on the lifetime of an LED in case a low current is supplied to the LED, and vice versa. Therefore, the lifetime of an LED can be influenced by varying the current through the LED depending on a measured temperature surrounding the LED.
- the average current is decreased with rising ambient temperatures and increased with falling ambient temperatures, in order to increasing the lifetime of an LED.
- the invention In comparison to a solution using for each required LED several LEDs with a lower current in order to reduce the degradation of the luminance intensity, the invention moreover requires less LEDs. Thus, the mechanical size and the costs of the device can be reduced. In addition, the power consumption will be lower, since one LED supplied with a high current requires less power than several LEDs supplied with a corresponding lower current.
- the current is controlled analogously, i.e. the forward current is changed linearly or in several steps as a function of the measured temperature.
- the forward current is changed linearly or in several steps as a function of the measured temperature.
- Such a direct current control has the disadvantage that in some cases a change of the forward current may result in a change of the LED color.
- the current is controlled digitally.
- the LED forward current is kept constant, but the current is pulsed, i.e. it is turned on and off e.g. over a hundred times per second.
- the average current is then adapted to the measured temperature by changing the duty ratio of the pulsing.
- the duty ratio determines the ratio between the time in which a current is provided, i.e. the total length of the pulses, and the time in which a current is not provided, i.e. the total length between the pulses.
- the duty ratio of the pulsing determines the average current and therefore the luminous intensity.
- the LED average current will be 50% of the value without any pulsing. Therefore, the luminous intensity is the same as with a constant current reduced to 50%.
- the luminous intensity follows the current almost linearly at a given ambient temperature.
- the pulsing can be realized in several ways. It can moreover be achieved by measures on the anode side of the LED, at which the current is provided, or by measures on the cathode side of an LED.
- switching means like a transistor, e.g. a FET (field effect transistor), can be employed for realizing the pulsing.
- the switching means can connect the cathode of the LED to ground, and for turning the LED off, the switching means can connect the LED to a high voltage.
- the high voltage should be as close as possible to LED supply voltage, in order to avoid that any current passes the LED.
- the LED can be turned on and off by a pulsing element controlling the power supply to the LED.
- a power supply circuit or some other driver providing power to the LED can be pulsed between shut down and enable states by a pulsing element, e.g. by an active current control.
- a pulsing element e.g. by an active current control.
- Several LEDs in series may also be supplied with a pulsed current this way.
- the pulsing element can be controlled for example by an engine IC.
- Engine ICs are employed e.g. in mobile phones for data processing.
- the pulsing element can even be integrated into such an engine IC.
- the pulsing element can be controlled by an LED driver or be integrated into an LED driver.
- the ambient temperature surrounding an LED can be measured according to the invention with a temperature-sensing element.
- the temperature sensing element can be arranged at any suitable place in, on or close to a device comprising at least one LED that is to be operated.
- the temperature-sensing element can also be integrated into some other unit of the device, like an engine IC or an LED driver.
- the measurement results of a temperature sensing element may be evaluated by a software of the engine IC for controlling a pulsing element employed for supplying a pulsed current to the LED.
- an LED driver or any other processing unit in a device with the at least one LED that is to be operated can evaluate the temperature information from the temperature sensing element.
- an engine IC does not need to control the LED current, or sense the temperature.
- FIGURE shows a simplified block diagram of an exemplary embodiment of a device according to the invention.
- FIGURE shows a block diagram with selected elements of an embodiment of a device according to the invention comprising an LED arrangement 1 .
- the device can be for instance a mobile phone, in which the LED arrangement is employed for the display.
- a temperature sensor 2 is arranged close to the LED arrangement 1 .
- the output of the temperature sensor 2 is connected to an input of a phone engine IC 3 .
- the output of the engine IC 3 is connected to an input of an LED driver 4 .
- the LED driver 4 comprises a pulsing element 5 , and is further connected to the LED arrangement 1 .
- the ambient temperature surrounding the LED arrangement is detected with the temperature sensor 2 .
- the measurement results of the temperature sensor 2 are read by the engine IC 3 of the mobile phone.
- the engine IC 3 comprises a software for processing the received measurement results.
- This software determines the current ambient temperature out of the received measurement results. Based on the determined temperature, the software then calculates a duty ratio for pulsing a current that is to be supplied to the LED arrangement. The ratio is calculated such that it is lower the higher the temperature is determined. The calculated duty ratio is then forwarded to the LED driver 4 .
- the LED driver 4 is responsible for supplying the LED arrangement 1 with a current adapted to the ambient temperature.
- the pulsing element integrated in the LED driver 4 is able to pulse an available current with a variable duty ratio, which variable duty ratio is set to the duty ratio provided by the engine IC 3 .
- the LED driver 4 supplies the pulsed current to the LED arrangement 1 .
- the higher the duty ratio provided by the engine IC 3 the larger the portion of time during which pulses of the same amplitude are supplied within one second to the LED arrangement 1 .
- the LED arrangement 1 is supplied with a current of which a short-term average is inversely proportional to the ambient temperature surrounding the LED arrangement 1 . As a consequence, a rapid degradation of the luminous intensity provided by the LED arrangement 1 is prevented.
Abstract
The invention relates to a method for operating a light emitting diode (LED). In order to enable an influence on the lifetime of the LED, it is proposed that the method comprises measuring the ambient temperature surrounding the LED, and controlling a current through the LED depending on the measured temperature. The invention equally relates to a corresponding device comprising at least one LED 1. It is proposed that this devices further comprises a temperature sensing element 2 for measuring the ambient temperature surrounding the at least one LED 1, and controlling means 3 for controlling a current flowing through said at least one LED 1 depending on the measured temperature.
Description
- This application claims priority under 35 USC §119(e) to European Patent Application No. 01 127 555.9 filed on Nov. 19, 2001.
- The invention relates to a method for operating a light emitting diode (LED). The invention equally relates to a device comprising at least one LED.
- The use of LEDs is well known in the art. LEDs are also employed in a great variety of applications, for example in a display or a keypad lighting of a user interface hardware.
- The intensity of the light emitted by an LED correlates with the level of a supplied current. Additionally, however, the luminous intensity of LEDs is subject to a degradation over time. The degradation rate and therefore the useful lifetime of an LED depends on the power over the LED. The power over the LED, in turn, depends on the forward current supplied to the LED and on the ambient temperature surrounding the LED. Thus, on the one hand, the luminous intensity of an LED supplied with a high current can degrade relatively fast. On the other hand, the luminous intensity of an LED can degrade rather quickly in case of a high ambient temperature, in particular in case of an ambient temperature which is higher than a maximum temperature specified in the respective LED specification.
- A correlation between the power over LEDs and the temperature surrounding these LEDs has also been addressed in the document JP 2001043728, which aims at avoiding fluctuations in the light quality due to changes in temperature. In this document, a light emitting diode lighting system is described, in which a plurality of LEDs is arranged on a heat radiating plate. The LEDs emit light due to current pulses supplied by an LED driver. In order to avoid fluctuations in the light quality, it is proposed that the temperature of the heat radiating plate is regulated by thermo modules absorbing heat on the heat radiating plate.
- Suppressing a rise in the ambient temperature would also be suited for increasing the lifetime of an LED. In many cases, however, for example in mobile phones, it is not possible to ensure that the ambient temperature does not exceed a maximum value that is allowed for the LED with the employed forward current.
- In known applications, the problem is either ignored, or several LEDs with a low current are employed instead of one LED with a high current, in order to reduce the power over the single LEDs.
- It is an object of the invention to enable an influence on the lifetime of an LED. It is in particular an object of the invention to provide a possibility for preventing a rapid aging of an LED that may be exposed to high ambient temperatures, and more specifically for preventing a fast degradation of the luminous intensity of such an LED.
- These objects are reached on the one hand with a method for operating an LED. It is proposed for such a method that in a first step the ambient temperature surrounding the LED is measured. It is further proposed that in a second step, a current through the LED is controlled depending on the measured temperature.
- On the other hand, the objects are reached with a device comprising at least one LED. It is proposed that the device further comprises a temperature sensing element for measuring the ambient temperature surrounding the at least one LED, and controlling means for controlling a current flowing through the at least one LED depending on the measured temperature.
- The invention proceeds from the idea that the luminous intensity and thus the lifetime of an LED depend in particular on the respective combination of the current through the LED and the ambient temperature. More specifically, a high ambient temperature has less influence on the lifetime of an LED in case a low current is supplied to the LED, and vice versa. Therefore, the lifetime of an LED can be influenced by varying the current through the LED depending on a measured temperature surrounding the LED.
- It is proposed in particular that the average current is decreased with rising ambient temperatures and increased with falling ambient temperatures, in order to increasing the lifetime of an LED.
- It is an advantage of the invention that the full luminous intensity of an LED can be made available for a longer time, while at the same time an optimal output depending on the present temperature situation can be guaranteed.
- Further, there is a lower risk that an LED deteriorates so much that a repair becomes necessary. As a result, also the satisfaction of the user is increased.
- In comparison to a solution using for each required LED several LEDs with a lower current in order to reduce the degradation of the luminance intensity, the invention moreover requires less LEDs. Thus, the mechanical size and the costs of the device can be reduced. In addition, the power consumption will be lower, since one LED supplied with a high current requires less power than several LEDs supplied with a corresponding lower current.
- Preferred embodiments of the invention become apparent from the subclaims.
- There are several possibilities for controlling the current through an LED.
- In a first alternative, the current is controlled analogously, i.e. the forward current is changed linearly or in several steps as a function of the measured temperature. Such a direct current control has the disadvantage that in some cases a change of the forward current may result in a change of the LED color.
- In a second, preferred alternative, which avoids the problem of changing colors, the current is controlled digitally. In this alternative, the LED forward current is kept constant, but the current is pulsed, i.e. it is turned on and off e.g. over a hundred times per second. The average current is then adapted to the measured temperature by changing the duty ratio of the pulsing. The duty ratio determines the ratio between the time in which a current is provided, i.e. the total length of the pulses, and the time in which a current is not provided, i.e. the total length between the pulses.
- For the human eye, the duty ratio of the pulsing determines the average current and therefore the luminous intensity. With a 50% duty ratio for instance, the LED average current will be 50% of the value without any pulsing. Therefore, the luminous intensity is the same as with a constant current reduced to 50%. The luminous intensity follows the current almost linearly at a given ambient temperature.
- The pulsing can be realized in several ways. It can moreover be achieved by measures on the anode side of the LED, at which the current is provided, or by measures on the cathode side of an LED.
- On the cathode side of an LED, switching means like a transistor, e.g. a FET (field effect transistor), can be employed for realizing the pulsing. For turning the LED on, the switching means can connect the cathode of the LED to ground, and for turning the LED off, the switching means can connect the LED to a high voltage. The high voltage should be as close as possible to LED supply voltage, in order to avoid that any current passes the LED.
- On the anode side of an LED, the LED can be turned on and off by a pulsing element controlling the power supply to the LED.
- To this end, a power supply circuit or some other driver providing power to the LED can be pulsed between shut down and enable states by a pulsing element, e.g. by an active current control. Several LEDs in series may also be supplied with a pulsed current this way.
- The pulsing element can be controlled for example by an engine IC. Engine ICs are employed e.g. in mobile phones for data processing. The pulsing element can even be integrated into such an engine IC. Alternatively the pulsing element can be controlled by an LED driver or be integrated into an LED driver.
- The ambient temperature surrounding an LED can be measured according to the invention with a temperature-sensing element. The temperature sensing element can be arranged at any suitable place in, on or close to a device comprising at least one LED that is to be operated. The temperature-sensing element can also be integrated into some other unit of the device, like an engine IC or an LED driver.
- If an engine IC is present in a device with the at least one LED that is to be operated, the measurement results of a temperature sensing element may be evaluated by a software of the engine IC for controlling a pulsing element employed for supplying a pulsed current to the LED.
- Alternatively, an LED driver or any other processing unit in a device with the at least one LED that is to be operated can evaluate the temperature information from the temperature sensing element. In this case, an engine IC does not need to control the LED current, or sense the temperature.
- In the following, the invention is explained in more detail with reference to a drawing. The only FIGURE shows a simplified block diagram of an exemplary embodiment of a device according to the invention.
- The only FIGURE shows a block diagram with selected elements of an embodiment of a device according to the invention comprising an
LED arrangement 1. The device can be for instance a mobile phone, in which the LED arrangement is employed for the display. - In the device, a
temperature sensor 2 is arranged close to theLED arrangement 1. The output of thetemperature sensor 2 is connected to an input of aphone engine IC 3. The output of theengine IC 3 is connected to an input of anLED driver 4. TheLED driver 4 comprises apulsing element 5, and is further connected to theLED arrangement 1. - For operating the
LED arrangement 1 with an appropriate current, the ambient temperature surrounding the LED arrangement is detected with thetemperature sensor 2. The measurement results of thetemperature sensor 2 are read by theengine IC 3 of the mobile phone. - The
engine IC 3 comprises a software for processing the received measurement results. This software determines the current ambient temperature out of the received measurement results. Based on the determined temperature, the software then calculates a duty ratio for pulsing a current that is to be supplied to the LED arrangement. The ratio is calculated such that it is lower the higher the temperature is determined. The calculated duty ratio is then forwarded to theLED driver 4. - The
LED driver 4 is responsible for supplying theLED arrangement 1 with a current adapted to the ambient temperature. To this end, the pulsing element integrated in theLED driver 4 is able to pulse an available current with a variable duty ratio, which variable duty ratio is set to the duty ratio provided by theengine IC 3. TheLED driver 4 supplies the pulsed current to theLED arrangement 1. The higher the duty ratio provided by theengine IC 3, the larger the portion of time during which pulses of the same amplitude are supplied within one second to theLED arrangement 1. - Thus, the
LED arrangement 1 is supplied with a current of which a short-term average is inversely proportional to the ambient temperature surrounding theLED arrangement 1. As a consequence, a rapid degradation of the luminous intensity provided by theLED arrangement 1 is prevented. - It is to be noted that the proposed embodiment of a device and of a method according the invention can be amended in any suitable way.
Claims (18)
1. A method for operating a light emitting diode (LED, 1), which method comprises measuring the ambient temperature surrounding said LED (1), and controlling a current flowing through said LED (1) depending on the measured temperature.
2. A method according to claim 1 , wherein said current through said LED (1) is controlled in a way that the higher the measured temperature, the lower is the average current through the LED (1).
3. A method according to claim 1 , wherein said current flowing through said LED (1) is a continuous current, and wherein said current is varied analogously depending on the measured temperature.
4. A method according to claim 1 , wherein said current flowing through said LED (1) is a pulsed current, which pulsed current is controlled by controlling the duty ratio of the pulsing depending on the measured temperature.
5. A method according to claim 1 , wherein said current is controlled on the cathode side of said LED (1).
6. A method according to claim 1 , wherein said current is controlled on the anode side of said LED (1).
7. A device comprising at least one light emitting diode (LED,1), a temperature sensing element (2) for measuring the ambient temperature surrounding the at least one LED, and controlling means (3) for controlling a current flowing through said at least one LED (1) depending on the measured temperature.
8. A device according to claim 7 , further comprising a pulsing element (5) for pulsing a current flowing through said at least one LED (1), which pulsing element is controlled by said controlling means (3) depending on the measured temperature.
9. A device according to claim 7 , wherein said current flowing through said at least one LED is controlled on the side of the cathode of the at least one LED depending on the measured temperature.
10. A device according to claim 9 , comprising switching means for pulsing the current flowing through said at least one LED, wherein said switching means connect the cathode of said at least one LED to ground for turning said at least one LED on and connect said cathode of said at least one LED to a predetermined voltage for turning said at least one LED off, and wherein said switching means are controlled by said controlling means depending on the measured temperature.
11. A device according to claim 7 , wherein said current flowing through said at least one LED (1) is controlled on the side of the anode of said at least one LED (1) depending on the measured temperature.
12. A device according to claim 11 , comprising an LED driver (4) for supplying a current to said at least one LED (1), which LED driver (4) includes a pulsing element (5) for pulsing said current supplied to said at least one LED (1), which pulsing element (5) is controlled by said controlling means (3) depending on the measured temperature.
13. A device according to claim 11 , comprising an engine IC, which engine IC includes a pulsing element for pulsing a current supplied to said at least one LED, which pulsing element is controlled by said controlling means depending on the measured temperature.
14. A device according to claim 7 , wherein said controlling means is an engine IC (3), which engine IC has access to the measurement results of the temperature sensing element (2).
15. A device according to claim 14 , wherein said engine IC comprises said temperature sensing element.
16. A device according to claim 7 , wherein said controlling means is an LED driver, which LED driver has access to the measurement results of the temperature sensing element.
17. A device according to claim 16 , wherein said LED driver comprises said temperature-sensing element.
18. A device according to claim 7 , wherein said at least one LED (1) is part of a display or of a keypad lighting of a user interface hardware.
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP01127555A EP1313353A1 (en) | 2001-11-19 | 2001-11-19 | Method and device for operating a light emitting diode |
EPEP01127555.9 | 2001-11-19 |
Publications (1)
Publication Number | Publication Date |
---|---|
US20030123521A1 true US20030123521A1 (en) | 2003-07-03 |
Family
ID=8179286
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US10/300,693 Abandoned US20030123521A1 (en) | 2001-11-19 | 2002-11-19 | Operating a light emitting diode |
Country Status (2)
Country | Link |
---|---|
US (1) | US20030123521A1 (en) |
EP (1) | EP1313353A1 (en) |
Cited By (19)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20060280224A1 (en) * | 2002-01-04 | 2006-12-14 | Kelvin Shih | LED junction temperature tester |
US20070040696A1 (en) * | 2005-08-18 | 2007-02-22 | Honeywell International Inc. | Aerospace light-emitting diode (LED)-based lights life and operation monitor compensator |
US20080111799A1 (en) * | 2004-05-25 | 2008-05-15 | Koninklijke Philips Electronics, N.V. | Driving an electroluminescent display |
US20090284155A1 (en) * | 2008-05-13 | 2009-11-19 | Reed William G | Gas-discharge lamp replacement |
US20100176746A1 (en) * | 2009-01-13 | 2010-07-15 | Anthony Catalano | Method and Device for Remote Sensing and Control of LED Lights |
US20100231136A1 (en) * | 2009-03-13 | 2010-09-16 | Led Specialists Inc. | Line voltage dimmable constant current led driver |
US20100277082A1 (en) * | 2009-05-01 | 2010-11-04 | Reed William G | Gas-discharge lamp replacement with passive cooling |
US20110115400A1 (en) * | 2009-11-17 | 2011-05-19 | Harrison Daniel J | Led dimmer control |
US9192011B2 (en) | 2011-12-16 | 2015-11-17 | Terralux, Inc. | Systems and methods of applying bleed circuits in LED lamps |
US9241401B2 (en) | 2010-06-22 | 2016-01-19 | Express Imaging Systems, Llc | Solid state lighting device and method employing heat exchanger thermally coupled circuit board |
US9265119B2 (en) | 2013-06-17 | 2016-02-16 | Terralux, Inc. | Systems and methods for providing thermal fold-back to LED lights |
US9326346B2 (en) | 2009-01-13 | 2016-04-26 | Terralux, Inc. | Method and device for remote sensing and control of LED lights |
US9342058B2 (en) | 2010-09-16 | 2016-05-17 | Terralux, Inc. | Communication with lighting units over a power bus |
US9445485B2 (en) | 2014-10-24 | 2016-09-13 | Express Imaging Systems, Llc | Detection and correction of faulty photo controls in outdoor luminaires |
US9572230B2 (en) | 2014-09-30 | 2017-02-14 | Express Imaging Systems, Llc | Centralized control of area lighting hours of illumination |
US9596738B2 (en) | 2010-09-16 | 2017-03-14 | Terralux, Inc. | Communication with lighting units over a power bus |
US10164374B1 (en) | 2017-10-31 | 2018-12-25 | Express Imaging Systems, Llc | Receptacle sockets for twist-lock connectors |
US11375599B2 (en) | 2017-04-03 | 2022-06-28 | Express Imaging Systems, Llc | Systems and methods for outdoor luminaire wireless control |
US11653436B2 (en) | 2017-04-03 | 2023-05-16 | Express Imaging Systems, Llc | Systems and methods for outdoor luminaire wireless control |
Families Citing this family (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE102004028987A1 (en) * | 2004-06-16 | 2006-01-05 | Volkswagen Ag | Illumination unit controlling method for motor vehicle, involves increasing or decreasing duty cycle of pulse width modulation when ambient temperature increases or decreases, for adjusting light emission within maximum and minimum values |
DE102004055884A1 (en) * | 2004-11-19 | 2006-05-24 | Audi Ag | Lighting device for a motor vehicle comprising one or more LEDs |
EP2066149A3 (en) | 2007-11-27 | 2009-08-19 | Stefan Ruppel | Flat LED lights with heat-dispersing board, in particular for furniture |
EP2073607A1 (en) * | 2007-12-19 | 2009-06-24 | Data Display GmbH | LED-controller for optimizing LED lifetime |
GB2457101A (en) * | 2008-02-04 | 2009-08-05 | Hao-Chin Pai | LED driver circuit with current, voltage, and temperature regulation |
DE102008017483A1 (en) | 2008-04-03 | 2009-10-08 | Steinel Gmbh | A lighting device |
DE102008018808A1 (en) * | 2008-04-15 | 2009-10-22 | Ledon Lighting Jennersdorf Gmbh | Microcontroller optimized pulse width modulation (PWM) control of a light emitting diode (LED) |
DE102008058524B4 (en) * | 2008-11-21 | 2010-11-18 | Herbert Waldmann Gmbh & Co. Kg | Circuit arrangement for a light with LEDs |
Citations (23)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5206778A (en) * | 1991-05-16 | 1993-04-27 | International Business Machines Corporation | Sense circuit for on-chip thermal shutdown |
US5406172A (en) * | 1993-12-28 | 1995-04-11 | Honeywell Inc. | Light source intensity control device |
US5451979A (en) * | 1993-11-04 | 1995-09-19 | Adaptive Micro Systems, Inc. | Display driver with duty cycle control |
US5697705A (en) * | 1994-02-09 | 1997-12-16 | Test Products, Inc. | Method for testing a heat source |
US5757008A (en) * | 1995-11-08 | 1998-05-26 | Nikon Corporation | Infrared-ray image sensor |
US5859658A (en) * | 1995-10-19 | 1999-01-12 | Xerox Corporation | LED printbar aging compensation using I-V slope characteristics |
US5912568A (en) * | 1997-03-21 | 1999-06-15 | Lucent Technologies Inc. | Led drive circuit |
US6107985A (en) * | 1997-10-30 | 2000-08-22 | Ericsson Inc. | Backlighting circuits including brownout detection circuits responsive to a current through at least one light emitting diode and related methods |
US6111739A (en) * | 1999-08-11 | 2000-08-29 | Leotek Electronics Corporation | LED power supply with temperature compensation |
US6147699A (en) * | 1998-11-10 | 2000-11-14 | Lexmark International, Inc. | Low electromagnetic emissions and improved signal quality video drive architecture for laser printers |
US6161910A (en) * | 1999-12-14 | 2000-12-19 | Aerospace Lighting Corporation | LED reading light |
US6188571B1 (en) * | 1997-11-03 | 2001-02-13 | Aiwa Raid Technology, Inc. | High density RAID subsystem with highly integrated controller |
US6349023B1 (en) * | 2000-02-24 | 2002-02-19 | Robotic Vision Systems, Inc. | Power control system for illumination array |
US6362740B1 (en) * | 1999-11-11 | 2002-03-26 | Samsung Electronics Co., Ltd. | Apparatus for providing thermal alert signal and control method thereof in skin-contact type terminal |
US6400101B1 (en) * | 1999-06-30 | 2002-06-04 | Patent-Treuhand-Gesellschaft Fuer Elektrische Gluehlampen Mbh | Control circuit for LED and corresponding operating method |
US6400102B1 (en) * | 1999-12-23 | 2002-06-04 | Gelcore, Llc | Non-linear light-emitting load current control |
US20020103022A1 (en) * | 2001-02-01 | 2002-08-01 | Somol Jessica Thompson | Systems and methods for limiting a total amount won by a player based on the player's performance in a game of skill |
US20020130786A1 (en) * | 2001-01-16 | 2002-09-19 | Visteon Global Technologies,Inc. | Series led backlight control circuit |
US6459919B1 (en) * | 1997-08-26 | 2002-10-01 | Color Kinetics, Incorporated | Precision illumination methods and systems |
US20020140880A1 (en) * | 2001-01-16 | 2002-10-03 | Weindorf Paul F.L. | LED backlighting system |
US6609655B1 (en) * | 2000-06-26 | 2003-08-26 | Martha F. Harrell | Smart card system for providing financial, travel, and entertainment-related services |
US20030169226A1 (en) * | 2002-01-23 | 2003-09-11 | Seiko Epson Corporation | Backlight control device for liquid crystal display |
US20030214506A1 (en) * | 2002-05-10 | 2003-11-20 | Metod Koselj | Graphics engine, and display driver IC and display module incorporating the graphics engine |
Family Cites Families (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE19602891A1 (en) * | 1996-01-27 | 1997-08-07 | Kammerer Gmbh M | Method and arrangement for adjusting the brightness of a current- or voltage-controlled illuminant for backlighting a display, in particular for motor vehicles |
US5783909A (en) * | 1997-01-10 | 1998-07-21 | Relume Corporation | Maintaining LED luminous intensity |
DE19728763B4 (en) * | 1997-07-07 | 2007-10-31 | Reitter & Schefenacker Gmbh & Co. Kg | Circuit device for protecting current-driven light sources, in particular LEDs, for signaling or lighting purposes |
JP2001043728A (en) * | 1999-07-30 | 2001-02-16 | Fujitsu Takamisawa Component Ltd | Light emitting diode lighting system |
DE19943345A1 (en) * | 1999-09-10 | 2001-03-15 | Hella Kg Hueck & Co | LED light |
-
2001
- 2001-11-19 EP EP01127555A patent/EP1313353A1/en not_active Withdrawn
-
2002
- 2002-11-19 US US10/300,693 patent/US20030123521A1/en not_active Abandoned
Patent Citations (24)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5206778A (en) * | 1991-05-16 | 1993-04-27 | International Business Machines Corporation | Sense circuit for on-chip thermal shutdown |
US5451979A (en) * | 1993-11-04 | 1995-09-19 | Adaptive Micro Systems, Inc. | Display driver with duty cycle control |
US5406172A (en) * | 1993-12-28 | 1995-04-11 | Honeywell Inc. | Light source intensity control device |
US5697705A (en) * | 1994-02-09 | 1997-12-16 | Test Products, Inc. | Method for testing a heat source |
US5859658A (en) * | 1995-10-19 | 1999-01-12 | Xerox Corporation | LED printbar aging compensation using I-V slope characteristics |
US5757008A (en) * | 1995-11-08 | 1998-05-26 | Nikon Corporation | Infrared-ray image sensor |
US5912568A (en) * | 1997-03-21 | 1999-06-15 | Lucent Technologies Inc. | Led drive circuit |
US6459919B1 (en) * | 1997-08-26 | 2002-10-01 | Color Kinetics, Incorporated | Precision illumination methods and systems |
US6256007B1 (en) * | 1997-10-30 | 2001-07-03 | Ericsson Inc. | Radio communications devices with backlighting circuits having brownout detection circuits responsive to a current through a light emitting diode |
US6107985A (en) * | 1997-10-30 | 2000-08-22 | Ericsson Inc. | Backlighting circuits including brownout detection circuits responsive to a current through at least one light emitting diode and related methods |
US6188571B1 (en) * | 1997-11-03 | 2001-02-13 | Aiwa Raid Technology, Inc. | High density RAID subsystem with highly integrated controller |
US6147699A (en) * | 1998-11-10 | 2000-11-14 | Lexmark International, Inc. | Low electromagnetic emissions and improved signal quality video drive architecture for laser printers |
US6400101B1 (en) * | 1999-06-30 | 2002-06-04 | Patent-Treuhand-Gesellschaft Fuer Elektrische Gluehlampen Mbh | Control circuit for LED and corresponding operating method |
US6111739A (en) * | 1999-08-11 | 2000-08-29 | Leotek Electronics Corporation | LED power supply with temperature compensation |
US6362740B1 (en) * | 1999-11-11 | 2002-03-26 | Samsung Electronics Co., Ltd. | Apparatus for providing thermal alert signal and control method thereof in skin-contact type terminal |
US6161910A (en) * | 1999-12-14 | 2000-12-19 | Aerospace Lighting Corporation | LED reading light |
US6400102B1 (en) * | 1999-12-23 | 2002-06-04 | Gelcore, Llc | Non-linear light-emitting load current control |
US6349023B1 (en) * | 2000-02-24 | 2002-02-19 | Robotic Vision Systems, Inc. | Power control system for illumination array |
US6609655B1 (en) * | 2000-06-26 | 2003-08-26 | Martha F. Harrell | Smart card system for providing financial, travel, and entertainment-related services |
US20020130786A1 (en) * | 2001-01-16 | 2002-09-19 | Visteon Global Technologies,Inc. | Series led backlight control circuit |
US20020140880A1 (en) * | 2001-01-16 | 2002-10-03 | Weindorf Paul F.L. | LED backlighting system |
US20020103022A1 (en) * | 2001-02-01 | 2002-08-01 | Somol Jessica Thompson | Systems and methods for limiting a total amount won by a player based on the player's performance in a game of skill |
US20030169226A1 (en) * | 2002-01-23 | 2003-09-11 | Seiko Epson Corporation | Backlight control device for liquid crystal display |
US20030214506A1 (en) * | 2002-05-10 | 2003-11-20 | Metod Koselj | Graphics engine, and display driver IC and display module incorporating the graphics engine |
Cited By (32)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20060280224A1 (en) * | 2002-01-04 | 2006-12-14 | Kelvin Shih | LED junction temperature tester |
US20080111799A1 (en) * | 2004-05-25 | 2008-05-15 | Koninklijke Philips Electronics, N.V. | Driving an electroluminescent display |
US20070040696A1 (en) * | 2005-08-18 | 2007-02-22 | Honeywell International Inc. | Aerospace light-emitting diode (LED)-based lights life and operation monitor compensator |
WO2007022409A3 (en) * | 2005-08-18 | 2007-05-31 | Honeywell Int Inc | Aerospace light-emitting diode (led) - based lights life and operation monitor compensator |
US7391335B2 (en) | 2005-08-18 | 2008-06-24 | Honeywell International, Inc. | Aerospace light-emitting diode (LED)-based lights life and operation monitor compensator |
US20090284155A1 (en) * | 2008-05-13 | 2009-11-19 | Reed William G | Gas-discharge lamp replacement |
US8926138B2 (en) * | 2008-05-13 | 2015-01-06 | Express Imaging Systems, Llc | Gas-discharge lamp replacement |
US20100176746A1 (en) * | 2009-01-13 | 2010-07-15 | Anthony Catalano | Method and Device for Remote Sensing and Control of LED Lights |
US9560711B2 (en) | 2009-01-13 | 2017-01-31 | Terralux, Inc. | Method and device for remote sensing and control of LED lights |
US9326346B2 (en) | 2009-01-13 | 2016-04-26 | Terralux, Inc. | Method and device for remote sensing and control of LED lights |
US9161415B2 (en) | 2009-01-13 | 2015-10-13 | Terralux, Inc. | Method and device for remote sensing and control of LED lights |
US8358085B2 (en) | 2009-01-13 | 2013-01-22 | Terralux, Inc. | Method and device for remote sensing and control of LED lights |
US8686666B2 (en) | 2009-01-13 | 2014-04-01 | Terralux, Inc. | Method and device for remote sensing and control of LED lights |
US20100231136A1 (en) * | 2009-03-13 | 2010-09-16 | Led Specialists Inc. | Line voltage dimmable constant current led driver |
US8310171B2 (en) | 2009-03-13 | 2012-11-13 | Led Specialists Inc. | Line voltage dimmable constant current LED driver |
US20100277082A1 (en) * | 2009-05-01 | 2010-11-04 | Reed William G | Gas-discharge lamp replacement with passive cooling |
US8926139B2 (en) | 2009-05-01 | 2015-01-06 | Express Imaging Systems, Llc | Gas-discharge lamp replacement with passive cooling |
US20110121760A1 (en) * | 2009-11-17 | 2011-05-26 | Harrison Daniel J | Led thermal management |
US20110121751A1 (en) * | 2009-11-17 | 2011-05-26 | Harrison Daniel J | Led power-supply detection and control |
US10485062B2 (en) | 2009-11-17 | 2019-11-19 | Ledvance Llc | LED power-supply detection and control |
US20110115400A1 (en) * | 2009-11-17 | 2011-05-19 | Harrison Daniel J | Led dimmer control |
US9668306B2 (en) | 2009-11-17 | 2017-05-30 | Terralux, Inc. | LED thermal management |
US9241401B2 (en) | 2010-06-22 | 2016-01-19 | Express Imaging Systems, Llc | Solid state lighting device and method employing heat exchanger thermally coupled circuit board |
US9596738B2 (en) | 2010-09-16 | 2017-03-14 | Terralux, Inc. | Communication with lighting units over a power bus |
US9342058B2 (en) | 2010-09-16 | 2016-05-17 | Terralux, Inc. | Communication with lighting units over a power bus |
US9192011B2 (en) | 2011-12-16 | 2015-11-17 | Terralux, Inc. | Systems and methods of applying bleed circuits in LED lamps |
US9265119B2 (en) | 2013-06-17 | 2016-02-16 | Terralux, Inc. | Systems and methods for providing thermal fold-back to LED lights |
US9572230B2 (en) | 2014-09-30 | 2017-02-14 | Express Imaging Systems, Llc | Centralized control of area lighting hours of illumination |
US9445485B2 (en) | 2014-10-24 | 2016-09-13 | Express Imaging Systems, Llc | Detection and correction of faulty photo controls in outdoor luminaires |
US11375599B2 (en) | 2017-04-03 | 2022-06-28 | Express Imaging Systems, Llc | Systems and methods for outdoor luminaire wireless control |
US11653436B2 (en) | 2017-04-03 | 2023-05-16 | Express Imaging Systems, Llc | Systems and methods for outdoor luminaire wireless control |
US10164374B1 (en) | 2017-10-31 | 2018-12-25 | Express Imaging Systems, Llc | Receptacle sockets for twist-lock connectors |
Also Published As
Publication number | Publication date |
---|---|
EP1313353A1 (en) | 2003-05-21 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
US20030123521A1 (en) | Operating a light emitting diode | |
JP3984214B2 (en) | Light emission control device | |
US8659235B2 (en) | Process and circuitry for controlling a load | |
KR100897819B1 (en) | Circuit for driving Light Emitted Diode | |
US6127784A (en) | LED driving circuitry with variable load to control output light intensity of an LED | |
TWI391028B (en) | Light emitting diode module | |
US7656100B2 (en) | System for temperature prioritised colour controlling of a solid-state lighting unit | |
EP1701589B1 (en) | Electric circuit and method for monitoring a temperature of a light emitting diode | |
US8536933B2 (en) | Method and circuit for an operating area limiter | |
US20080122383A1 (en) | Led driver | |
JP4722649B2 (en) | LED light source device | |
KR20080063372A (en) | A method of compensating an aging process of an illumination device | |
JP2007066897A (en) | Led light source for back-lighting using integrated electronic equipment | |
EP2073607A1 (en) | LED-controller for optimizing LED lifetime | |
US7952297B2 (en) | Driving device for providing light dimming control of light-emitting element | |
US20120306386A1 (en) | Led drive device and led illuminating device | |
JP2002324685A (en) | Lighting device | |
JP2007109747A (en) | Led lighting controller | |
JP2010015728A (en) | Backlight dimming control device | |
JP2014220200A (en) | Illuminating device and control method thereof | |
US20070046660A1 (en) | Power supply circuit and electronic appliance therewith | |
JP5625370B2 (en) | Lighting control device and lighting device including the same | |
WO2006094590A1 (en) | Electric circuit and method for monitoring a temperature of a light emitting diode | |
US20160374165A1 (en) | Backlight module and liquid-crystal display device using the same | |
US20070268318A1 (en) | Light circuit |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
AS | Assignment |
Owner name: NOKIA CORPORATION, FINLAND Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:LUOMA, JUKKA;REEL/FRAME:013819/0767 Effective date: 20030121 |
|
STCB | Information on status: application discontinuation |
Free format text: ABANDONED -- FAILURE TO RESPOND TO AN OFFICE ACTION |